The present invention relates generally to interface devices between humans and computers, and more particularly to computer input devices that provide force feedback to the user.
Computer systems are used extensively in the home entertainment industry to implement video games, video simulations, and the like. In the video game industry, a video game computer system displays a visual game environment to a user on a display screen or other visual output device. Users can interact with the displayed environment to play a game, experience a simulation or xe2x80x9cvirtual realityxe2x80x9d environment, or otherwise influence events depicted on the screen. Such user interaction is implemented through the use of a human-computer interface device, such as a joystick, xe2x80x9cjoypadxe2x80x9d button controller, mouse, stylus and tablet, or the like, that is connected to the computer system controlling the game environment.
One common interface device to game environments is a joystick controller. A joystick usually includes a member for the user to grasp and move in one or more degrees of freedom. The user""s manipulations of the joystick are input to the computer system and the results or effects of these manipulations are typically displayed to the user on the display screen. While a standard joystick is effective in allowing a user to input commands to a game environment, it is limited to providing only input to the game computer system. The user can receive feedback about the results of his, or her actions only through the visual medium of the display screen and, usually, the auditory medium. A standard joystick cannot itself provide feedback information to the user. For example, if the simulated aircraft that the user is controlling in a game environment collides with another aircraft, the user only receives the visual and auditory feedback that such a collision occurred. The standard joystick has no means of conveying such collision information to the user.
Joysticks and other input devices have been developed to provide tactile (xe2x80x9chapticxe2x80x9d) feedback to a user, more generally known as xe2x80x9cforce feedback.xe2x80x9d These types of joysticks can provide physical sensations to the user manipulating the joystick. Typically, motors are coupled to the joystick and are connected to the controlling computer system. The computer system can provide forces on the joystick in conjunction with gaming events by controlling the motors. Through such a joystick, the computer system can convey to the user the physical sensation of colliding into a wall, moving through a liquid, driving over a bumpy road, and other sensations. The user can thus experience an entire sensory dimension in the gaming experience that was previously absent. Force feedback joysticks can provide a whole new modality for human-computer interaction.
Force feedback input devices of the prior art have concentrated on providing maximum haptic fidelity, i.e., the realism of the tactile feedback was desired to be optimized. This is because most of the force feedback devices have been targeted at the specific needs of highly industrial applications. To attain such realism, important design concerns such as size, weight, complexity, power consumption, programming compatibility, cost, aesthetics, and safety have been sacrificed. As a result, typical force feedback mechanisms are complex robotic mechanisms which require precision components, high speed interface electronics, and expensive actuators.
To provide realistic force feedback, the devices of the prior art typically use servo motors under computer control. Pneumatic and hydraulic devices are also used as actuators in force feedback devices. In pneumatic and hydraulic devices, a source of pressurized fluid is usually coupled to a piston in a cylinder, and the flow of the pressurized fluid is controlled by a computer system to provide active forces to the user. For example, a pneumatic system is described by Burdea et al. in U.S. Pat. No. 5,143,505, in which active pneumatic actuators are provided on an interface glove to provide force feedback to a user""s fingers. These systems regulate pressurized air to generate active forces to the user.
While the potential market and applications of force feedback controllers in the home video game industry is immense, a number of concerns face the potential providers of force feedback joysticks to the general public for video game and similar applications. Foremost among these concerns is the issue of user safety. Because a force feedback device can impart physical forces upon the user, the potential for injury must be carefully addressed. One type of potential injury is an impact injury, which is caused by a driving blow to the user from the joystick handle. Equally as important are repetitive motion injuries, which are debilitative injuries that are caused by moderate jarring of the user""s hand over an extended period of game play. Such injury issues must be resolved before force feedback joysticks can be practically sold to the general public.
In the prior art feedback controllers, active forces are directly applied to the user to provide an inherently unsafe controller. In addition, high accelerations are usually produced to provide a wide range of force signal frequencies and achieve the desired high realism. However, such accelerations are even more unsafe for a user operating the device. These joysticks and other devices are thus unfit for the home market of video games and the like.
Other concerns regarding force feedback joysticks include the efficiency of manufacturing and marketing the joysticks. The cost, complexity, reliability, and size of a force feedback joystick for home use should be practical enough to mass produce the devices. In addition, aesthetic concerns such as compactness and operating noise level of a force feedback device are of concern in the home market. Since the prior art feedback controllers are mainly addressed to specific applications in industry, most force feedback mechanisms are costly, large, heavy, have significant power requirements, are difficult to program for applications. The prior art devices require high speed control signals from a controlling computer for stability, which usually requires more expensive and complex electronics. In addition, the prior art force feedback devices are typically large and noisy. These factors provide many obstacles to the would-be manufacturer of force feedback joysticks to the home video game market.
For example, the pneumatic force feedback device of Burdea et al. mentioned above includes many disadvantages to a would-be provider of force feedback devices in the home video game industry. The force feedback interface of Burdea et al. requires a large interface box including bulky pressure regulators, pressurized air supply, and a large 24-volt power supply. The active pneumatic actuators of Burdea et al. require high speed control signals to operate effectively and provide stability. Finally, Burdea et al""s pneumatic actuators can potentially be dangerous for a user when strong or unexpected forces are generated on a user of the interface.
Therefore, a safer, less expensive, less complex, more compact, more reliable, easier programmed, more aesthetic alternative to force feedback interface devices is desired for certain applications.
The present invention provides a human/computer fluid-resistance interface device that provides force feedback to a user operating the device. The device includes computer-controlled pneumatic or hydraulic dampers that provide a modulated passive damping resistance to the motion of an object that is controlled by a user. The interface device of the present invention is inherently safer for a user, requires lower power, and is less costly to produce than active actuators and other types of pneumatic/hydraulic actuators.
More particularly, an apparatus of the present invention for interfacing the motion of an object with an electrical system includes a sensor, such as a digital encoder, that detects movement of an object along a degree of freedom and develops an electrical sensor signal for the electrical system. The sensor is coupled to the object in the preferred embodiment. The apparatus also includes a passive fluid-resistance mechanism, such as a pneumatic or hydraulic damper, coupled to the object to transmit a drag to the object along the degree of freedom and resist a movement of the object. The damper is responsive to an electrical resistance signal provided by the electrical system and, with the sensor, provides an electromechanical interface between the object and the electrical system. In the preferred embodiment, the object is a joystick controller.
In the preferred embodiment, the passive damper uses air (or a different gas) flow to control the damping resistance output by the damper. In alternate embodiments, the passive damper can be a hydraulic brake utilizing liquid flow. The passive damper includes a cylinder and a piston operative to move within the cylinder. A valve is included for regulating a flow of a fluid through the cylinder, the valve being controlled by a digital computing apparatus to transmit a variable drag to the movement of the object. The valve can be an on-off valve which provides only two magnitudes of drag to the object. These two magnitudes include negligible drag when the valve is open, and maximum drag when the valve is closed to allow substantially no movement of the object along the degree of freedom. The valve can alternatively be a variable valve that provides multiple magnitudes of drag to the object. A solenoid can be coupled to the valve to control the opening and closing of the valve from the digital computing apparatus. A gimbal mechanism or slotted yoke mechanism can be coupled between the object and the damper. A play mechanism can also be coupled between the damper and the object for providing a desired amount of play between the damper and the object along the degree of freedom. The play can include rotary backlash provided by a coupling coupled to the object and having a keyed bore which is smaller than a keyed shaft that is received by the keyed bore. The keyed shaft is coupled to the damper. The desired play allows the sensor to detect movement of the object even when maximum resistive force is applied to the object.
Another apparatus for interfacing the motion of an object with an electrical system in accordance with the present invention includes a gimbal mechanism providing a first revolute degree of freedom to an object engaged with the gimbal mechanism about an axis of rotation. The gimbal mechanism includes a closed loop five member linkage in a preferred embodiment. A sensor is rigidly coupled to the gimbal mechanism for sensing positions of the object along the first degree of freedom. A braking mechanism is coupled to the gimbal mechanism to create a passive damping resistance to movement of the object along the first degree of freedom. The braking mechanism provides the damping resistance by regulating the flow of a fluid. The braking mechanism and the sensor provide an electromechanical interface between the object and the electrical system. This electrical system preferably includes a digital processing system for providing a braking signal to the braking mechanism and for receiving an electrical signal from the sensor.
The gimbal mechanism preferably provides a second degree of freedom to the object about a second axis of rotation, and a second sensor senses positions of the object along the second degree of freedom. A second braking mechanism creates a passive damping resistance along the second degree of freedom by regulating the flow of a second fluid. The braking mechanism preferably includes a piston assembly and a valve, where the piston assembly includes a cylinder and a piston operative to move within the cylinder. A piston rod couples the piston to the object and includes two ends, each end connected by a ball joint.
A method for interfacing motion of an object with an electrical system includes providing an object having a degree of freedom. Positions of the object along the degree of freedom are sensed with a sensor and electrical signals are produced from the sensor. A resistance to movement of the object is created along the degree of freedom by controlling the flow of a fluid. The degree of freedom, can be a rotary degree of freedom or a linear degree of freedom. The step of creating a resistance to the object""s movement includes coupling a passive brake to the object. The passive brake can include a piston assembly and a valve to control the flow of the fluid. In an alternate embodiment, the brake can include a piston assembly having a cylinder and a piston. An electrorheological fluid is provided in the cylinder, and a voltage is applied to electrodes in the cylinder. The voltage induces an electric field, which, in turn, controls a viscosity of the electrorheological fluid and thereby allows the flow of the fluid to be regulated. A gimbal mechanism or slotted yoke mechanism can also be included to provide two or more degrees of freedom to the object. The gimbal mechanism can be a closed loop five member linkage.
In yet another embodiment of the present invention, a system for controlling an electromechanical interface apparatus manipulated by a user includes a digital computer system for receiving an input control signal and for providing an output control signal which updates a process, such as a simulation or video game process, in response to the input control signal. A passive damper for receiving the output control signal provides a resistive force along a degree of freedom to an object coupled to the passive damper. The object is preferably grasped and moved by the user. The resistive force is based on a flow of a fluid within the passive damper, and the flow of the fluid is based on information in the output control signal. The force resists a user force applied to the object by the user along the degree of freedom. A sensor detects motion of the object and outputs the input control signal including information representative of the position and motion of the object to the digital computer system.
Preferably, the digital computer updates a simulation process in response to the input control signal and displays a simulation (or video game) to the user on a display screen. The passive damper is a pneumatic or hydraulic brake that includes a piston assembly and valve for regulating the flow of the fluid. The digital computer system preferably regulates the fluid flow by controlling the valve. Preferably, a local processor is coupled between the digital computer system and the damper/sensor that receives the output control signal from said digital computer system and provides a second output control signal to the passive damper. The local processor also receives a second input control signal from the sensor and outputs the input control signal to the digital computer system. The local processor can provide the second output control signal to the passive damper in response to the position and motion of the object. This can be accomplished independently of the output control signal from the digital computer system in a xe2x80x9creflex process. A serial interface can output the output control signal from the computer system and can receive the input control signal to the computer system. A digital to analog converter can receive the output control signal, convert the output control signal to an analog control signal, and output the analog control signal to the passive damper. The output control signal can control the resistive force on the object to simulate the object moving into an obstacle, moving over a textured surface, or moving through a damping environment in accordance with the simulation or video game.
The force feedback of the present invention is provided by passive dampers, which do not generate forces on a user but instead provide a damping resistance to the motion of a joystick moved by a user. The present invention is thus inherently safe for a user to operate, In addition, the dampers require less power and slower control signals than active actuators such as active pneumatic or hydraulic actuators and motors. In addition, the dampers are less costly and require simpler computer control electronics than other types of passive actuators. These improvements allow a computer system to have accurate control over a low-cost, safe interface providing realistic force feedback.
These and other advantages of the present invention will become apparent to those skilled in the art upon a reading of the following specification of the invention and a study of the several figures of the drawing.